Turbine engines, and particularly gas or combustion turbine engines, are rotary engines that extract energy from a flow of combusted gases passing through the engine onto a multitude of rotating turbine blades.
A turbine engine includes but is not limited to, in serial flow arrangement, a forward fan assembly, an aft fan assembly, a high-pressure compressor for compressing air flowing through the engine, a combustor for mixing fuel with the compressed air such that the mixture may be ignited, and a high-pressure turbine. The high-pressure compressor, combustor and high-pressure turbine are sometimes collectively referred to as the core engine. In operation, the core engine generates combustion gases which are discharged downstream to a counter-rotating low-pressure turbine that extracts energy therefrom for powering the forward and aft fan assemblies.
In at least some turbine engines, at least one turbine rotates in an opposite direction than the other rotating components within the engine. In some implementations a counter-rotating low-pressure turbine includes an outer drum having a first set of stages that are rotatably coupled to the forward fan assembly, and an inner drum having an equal number of stages that is rotatably coupled to the aft fan assembly.
The outer drum can be spaced from an outer casing of the engine and require cooling therebetween.